The present invention relates to a new and improved construction of a double-wall facade or front element for buildings operating with an overpressure ventilating or air conditioning installation, wherein at the region of the one horizontal edge of the element there is provided at its inner wall a throughpassage opening for exhaust air and at the region of the other horizontal edge there is provided at its outer wall a blow-off or exhaust opening for the exhaust air, both of the aforementioned openings being in flow communication with one another through the agency of an intermediate space or compartment between the inner wall and the outer wall.
It has been found that the energy consumption for the ventilation or climatizing or conditioning of buildings or structures equipped with such facade elements is extremely low. In practice, with such facade elements the intermediate compartment or space between the inner wall and the outer wall is continuously wiped by the exhaust air which is to be ejected and after the escape of the exhaust air through the blow-off or exhaust opening such exhaust air continuously blows over the facade element, so that the outside climatic conditions and the inside climatic conditions are always separated by two extremely effective convection barriers.
While this very effective insulation (in the case of facade elements provided with window openings covered by glass panes there is attained a coefficient of heat transfer k, related to the entire facade element, of only 0.3 to 1 kcal/m.sup.2 h.degree. C) works extremely well particularly in the case of external or ambient temperatures at the region of the freezing point or therebelow, in the case of pronounced temperature gradients there arise phenomena which are capable of impairing the properties of such facade elements which are particularly favorable with respect to the heat balance. These phenomena are dependent upon the condensation of the moisture of the exhaust air as soon as such, upon coming into direct contact with the outside air, is very rapidly cooled to the temperature thereof. It is to be conceived, for instance that with an inside of temperature of 25.degree.C and a relative humidity of 50 percent the moisture content of the air amounts to approximately 10 g/kg dry air, whereas with an air temperature of 0.degree.C the water content corresponding to saturation (relative humidity = 100 percent) is in the order of approximately 4 g/kg dry air. Hence, upon the ejection of the exhaust air considerable quantities of water condense, which when the temperatures are below the freezing point result in icing of complete portions of the facade and along therewith the impairment of the properties of the facade elements.